PSD Publications: No conditions. Results ordered -Date Deposited. 2016-12-10T03:25:52ZEPrintshttp://www.esrl.noaa.gov/images/banner_psd.pnghttp://www.esrl.noaa.gov/psd/pubs/13582012016-11-10T15:07:07Z2016-11-10T15:07:07Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1447This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14472016-11-10T15:07:07ZStochastic Parameterization: Towards a new view of Weather and Climate ModelsStochastic parameterizations - empirically derived, or based on rigorous mathematical and statistical concepts - have great potential to increase the predictive capability of next generation weather and climate models.
The last decade has seen the success of stochastic parameterizations in short-term, medium-range and seasonal forecasts: operational weather centers now routinely use stochastic parameterization schemes to better represent model inadequacy and improve the quantification of forecast uncertainty. Developed initially for numerical weather prediction, the inclusion of stochastic parameterizations not only provides better estimates of uncertainty, but it is also extremely promising for reducing longstanding climate biases and relevant for determining the climate response to external forcing.
This article highlights recent developments from different research groups which show that the stochastic representation of unresolved processes in the atmosphere, oceans, land surface and cryosphere of comprehensive weather and climate models (a) gives rise to more reliable probabilistic forecasts of weather and climate and (b) reduces systematic model bias.
We make a case that the use of mathematically stringent methods for the derivation of stochastic dynamic equations will lead to substantial improvements in our ability to accurately simulate weather and climate at all scales. Recent work in mathematics, statistical mechanics and turbulence is reviewed, its relevance for the climate problem demonstrated, and future research directions outlined.J. BernerU. AchatzL. Batté. . .C. Penlandet al.2016-11-10T14:34:15Z2016-11-10T14:34:38Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1446This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14462016-11-10T14:34:15ZThe magnitude of the snow-sourced reactive nitrogen flux to the boundary layer in the Uintah Basin, Utah, USAReactive nitrogen (Nr = NO, NO2, HONO) and volatile organic carbon emissions from oil and gas extraction activities play a major role in wintertime ground-level ozone exceedance events of up to 140 ppb in the Uintah Basin in eastern Utah. Such events occur only when the ground is snow covered, due to the impacts of snow on the stability and depth of the boundary layer and ultraviolet actinic flux at the surface. Recycling of reactive nitrogen from the photolysis of snow nitrate has been observed in polar and mid-latitude snow, but snow-sourced reactive nitrogen fluxes in mid-latitude regions have not yet been quantified in the field. Here we present vertical profiles of snow nitrate concentration and nitrogen isotopes (δ15N) collected during the Uintah Basin Winter Ozone Study 2014 (UBWOS 2014), along with observations of insoluble light-absorbing impurities, radiation equivalent mean ice grain radii, and snow density that determine snow optical properties. We use the snow optical properties and nitrate concentrations to calculate ultraviolet actinic flux in snow and the production of Nr from the photolysis of snow nitrate. The observed δ15N(NO3−) is used to constrain modeled fractional loss of snow nitrate in a snow chemistry column model, and thus the source of Nr to the overlying boundary layer. Snow-surface δ15N(NO3−) measurements range from −5 to 10 ‰ and suggest that the local nitrate burden in the Uintah Basin is dominated by primary emissions from anthropogenic sources, except during fresh snowfall events, where remote NOx sources from beyond the basin are dominant. Modeled daily averaged snow-sourced Nr fluxes range from 5.6 to 71 × 107 molec cm−2 s−1 over the course of the field campaign, with a maximum noontime value of 3.1 × 109 molec cm−2 s−1. The top-down emission estimate of primary, anthropogenic NOx in Uintah and Duchesne counties is at least 300 times higher than the estimated snow NOx emissions presented in this study. Our results suggest that snow-sourced reactive nitrogen fluxes are minor contributors to the Nr boundary layer budget in the highly polluted Uintah Basin boundary layer during winter 2014.M. ZatkoJ. ErblandJ. Savarino. . .W. D. Neffet al.2016-11-07T19:09:37Z2016-11-07T19:09:37Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1445This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14452016-11-07T19:09:37ZToward Improving Ice Water Content and Snow-Rate Retrievals from Radars. Part I: X and W Bands, Emphasizing CloudSatMicrophysical data and radar reflectivities (Ze, −15 < Ze < 10 dB) measured from flights during the NASA Tropical Clouds, Convection, Chemistry and Climate field program are used to relate Ze at X and W band to measured ice water content (IWC). Because nearly collocated Ze and IWC were each directly measured, Ze–IWC relationships could be developed directly. Using the particle size distributions and ice particle masses evaluated based on the direct IWC measurements, reflectivity–snowfall rate (Ze–S) relationships were also derived. For −15 < Ze < 10 dB, the relationships herein yield larger IWC and S than given by the retrievals and earlier relationships. The sensitivity of radar reflectivity to particle size distribution and size-dependent mass, shape, and orientation introduces significant uncertainties in retrieved quantities since these factors vary substantially globally. To partially circumvent these uncertainties, a W-band Ze–S relationship is developed by relating four years of global CloudSat reflectivity observations measured immediately above the melting layer to retrieved rain rates at the base of the melting layer. The supporting assumptions are that the water mass flux is constant through the melting layer, that the air temperature is nearly 0°C, and that the retrieved rain rates are well constrained. Where Ze > 10 dB, this Ze–S relationship conforms well to earlier relationships, but for Ze < 10 dB it yields higher IWC and S. Because not all retrieval algorithms estimate either or both IWC and S, the authors use a large aircraft-derived dataset to relate IWC and S. The IWC can then be estimated from S and vice versa.A. J. HeymsfieldS. Y. MatrosovN. B. Wood2016-10-27T22:59:45Z2016-10-27T23:02:01Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1444This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14442016-10-27T22:59:45ZSurface-atmosphere decoupling limits accumulation at Summit, GreenlandDespite rapid melting in the coastal regions of the Greenland Ice Sheet, a significant area (~40%) of the ice sheet rarely experiences surface melting. In these regions, the controls on annual accumulation are poorly constrained owing to surface conditions (for example, surface clouds, blowing snow, and surface inversions), which render moisture flux estimates from myriad approaches (that is, eddy covariance, remote sensing, and direct observations) highly uncertain. Accumulation is partially determined by the temperature dependence of saturation vapor pressure, which influences the maximum humidity of air parcels reaching the ice sheet interior. However, independent proxies for surface temperature and accumulation from ice cores show that the response of accumulation to temperature is variable and not generally consistent with a purely thermodynamic control. Using three years of stable water vapor isotope profiles from a high altitude site on the Greenland Ice Sheet, we show that as the boundary layer becomes increasingly stable, a decoupling between the ice sheet and atmosphere occurs. The limited interaction between the ice sheet surface and free tropospheric air reduces the capacity for surface condensation to achieve the rate set by the humidity of the air parcels reaching interior Greenland. The isolation of the surface also acts to recycle sublimated moisture by recondensing it onto fog particles, which returns the moisture back to the surface through gravitational settling. The observations highlight a unique mechanism by which ice sheet mass is conserved, which has implications for understanding both past and future changes in accumulation rate and the isotopic signal in ice cores from Greenland.M. BerkelhammerD. C. NooneH. C. Steen-LarsenA. BaileyC. J. CoxM. S. O'NeillD. SchneiderK. SteffenJ. W. C. White2016-10-24T23:01:45Z2016-10-24T23:01:45Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1443This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14432016-10-24T23:01:45ZCharacteristic raindrop size retrievals from measurements of differences in vertical Doppler velocities at Ka- and W-band radar frequenciesA Ka (~35 GHz) -W (~94 GHz) band radar approach to retrieve profiles of characteristic raindrop sizes, such as mean mass-weighted drop diameters Dm, from measurements of the difference in the vertical Doppler velocities (DDV) is analyzed. This retrieval approach is insensitive to radar calibration errors, vertical air motions, and attenuation effects. The Dm – DDV relations are derived using long term measurements of drop size distributions (DSDs) from different observational sites and do not assume a functional DSD shape. Unambiguous retrievals using this approach are shown to be available in the Dm range of approximately 0.5 - 2 mm, with average uncertainties of around 21%. Potential retrieval ambiguities occurring when larger drop populations exist, can be avoided by using a Ka-band vertical Doppler velocity threshold. The performance of the retrievals is illustrated using a long predominantly stratiform rain event observed at the Atmospheric Radiation Measurement (ARM) Southern Great Plains site. Intercomparison of DDV-based estimates of characteristic raindrop sizes with independent estimates available from ground-based disdrometer measurements reveal good agreement, with a correlation coefficient of 0.88 and mean differences between radar and disdrometer based Dm of approximately 14% for the entire range of unambiguous retrievals. The Ka-W-band DDV method to retrieve mean mass-weighted drop sizes is applicable to measurements from new dual-wavelength ARM cloud radars which are being deployed at a variety of observational facilities. An illustration for the retrievals at the Oliktok point ARM facility is also given.S. Y. Matrosov2016-10-20T16:07:54Z2016-10-20T16:07:54Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1442This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14422016-10-20T16:07:54ZEvaluation of Multisensor Quantitative Precipitation Estimation in Russian River Basin
An important goal of combining weather radar with rain gauge data is to provide reliable estimates of rainfall rate and accumulation and to further identify intense precipitation and issue flood warnings. Scanning radars provide the ability to observe precipitation over wider areas within shorter timeframes compared to rain gauges, leading to improved situational awareness and more accurate and reliable warnings of future precipitation and flooding events. The focus of this study is on evaluating the performance of the multi-radar multi-sensor (MRMS) system with and without the impact of a local gap filling radar. The challenge of using radar and rain gauges to provide accurate rainfall estimates in complex terrain is investigated. The area of interest is the Russian River basin north of San Francisco, CA, which lies within the National Oceanic and Atmospheric Administration (NOAA) Hydrometeorology Testbed (HMT). In this complex mountainous terrain, the challenge of obtaining reliable quantitative precipitation estimations (QPEs) is hindered by beam blockage and overshooting, as well as the enhancement of rainfall on the windward side of mountain ranges. The effectiveness of several local radars, which include four S-band National Weather Service (NWS) Weather Surveillance Radar–1988 Doppler (WSR-88DP) radars and a C-band gap filling TV station radar (i.e., KPIX), are considered for deriving QPE over this region. The precipitation estimation methodologies used the MRMS algorithms and an independent KPIX-only (Z−RZ−R) based QPE algorithm. In addition, a time series analysis is conducted in order to illustrate the radar-gauge rainfall difference caused by radar beam height. The sampling relative to precipitation vertical structure is also considered in regards to the depth of the precipitation and the height of the bright band. The quantitative evaluation of different QPE products is presented.D. WillieH. ChenV. ChandrasekarR. CifelliC. CampbellD. W. ReynoldsS. Y. MatrosovY. Zhang2016-10-20T15:47:05Z2016-10-20T15:47:21Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1441This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14412016-10-20T15:47:05ZThe Role of Ocean Heat Transport in the Global Climate Response to Projected Arctic Sea Ice LossThe purpose of this study is to elucidate the individual and combined roles of thermodynamic and dynamic ocean–atmosphere coupling in the equilibrium global climate response to projected Arctic sea ice loss using a suite of experiments conducted with Community Climate System Model, version 4, at 1° latitude–longitude spatial resolution. The results highlight the contrasting spatial structures and partially compensating effects of thermodynamic and dynamic coupling. In combination, thermodynamic and dynamic coupling produce a response pattern that is largely symmetric about the equator, whereas thermodynamic coupling alone yields an antisymmetric response. The latter is characterized by an interhemispheric sea surface temperature (SST) gradient, with maximum warming at high northern latitudes decreasing toward the equator, which displaces the intertropical convergence zone (ITCZ) and Hadley circulation northward. In contrast, the fully coupled response shows enhanced warming at high latitudes of both hemispheres and along the equator; the equatorial warming is driven by anomalous ocean heat transport convergence and is accompanied by a narrow equatorward intensification of the northern and southern branches of the ITCZ. In both cases, the tropical precipitation response to Arctic sea ice loss feeds back onto the atmospheric circulation at midlatitudes via Rossby wave dynamics, highlighting the global interconnectivity of the coupled climate system. This study demonstrates the importance of ocean dynamics in mediating the equilibrium global climate response to Arctic sea ice loss.R. A. ThomasC. DeserL. Sun2016-10-19T21:03:14Z2016-10-28T21:47:48Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1440This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14402016-10-19T21:03:14ZAssessment and Applications of Distributed Hydrologic Model - Russian-Napa River Basins, CAN/AL. E. JohnsonC. HsuR. J. ZamoraR. Cifelli2016-10-19T20:44:52Z2016-10-19T20:44:52Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1439This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14392016-10-19T20:44:52ZAdvancing Polar Prediction Capabilities on Daily to Seasonal Time ScalesThe polar regions have been attracting more and more attention in recent years, fueled by the perceptible impacts of anthropogenic climate change. Polar climate change provides new opportunities, such as shorter shipping routes between Europe and East Asia, but also new risks such as the potential for industrial accidents or emergencies in ice-covered seas. Here, it is argued that environmental prediction systems for the polar regions are less developed than elsewhere. There are many reasons for this situation, including the polar regions being (historically) lower priority, with fewer in situ observations, and with numerous local physical processes that are less well represented by models. By contrasting the relative importance of different physical processes in polar and lower latitudes, the need for a dedicated polar prediction effort is illustrated. Research priorities are identified that will help to advance environmental polar prediction capabilities. Examples include an improvement of the polar observing system; the use of coupled atmosphere–sea ice–ocean models, even for short-term prediction; and insight into polar–lower-latitude linkages and their role for forecasting. Given the enormity of some of the challenges ahead, in a harsh and remote environment such as the polar regions, it is argued that rapid progress will only be possible with a coordinated international effort. More specifically, it is proposed to hold a Year of Polar Prediction (YOPP) from mid-2017 to mid-2019 in which the international research and operational forecasting communities will work together with stakeholders in a period of intensive observing, modeling, prediction, verification, user engagement, and educational activities.T. JungN. D. GordonP. Bauer. . .C. W. Fairallet al.2016-10-19T17:14:52Z2016-10-28T19:46:01Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1438This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14382016-10-19T17:14:52ZBenefits of an Advanced Quantitative Precipitation Information System: San Francisco Bay Area Case StudyA case study for the San Francisco Bay area provides the context for quantification of the benefits of an Advanced Quantitative Precipitation Information (AQPI) system. An AQPI would dovetail with the current NWS forecast operations to provide incrementally higher resolution monitoring of rainfall events and longer lead time forecasts. Decisions on investments to obtain an operational AQPI system require demonstration that the benefits exceed the costs. Estimation of benefits involves characterization of the spectrum of human and ecological activities in which Bay area residents participate, including avoidance of flood damages, maximizing water supplies, and enhancing ecological, recreational and transportation services. A reconnaissance-level regional resource accounting approach has been developed to quantify AQPI benefits. Taken by category about 60% of the benefits are for flood damage mitigation ($37M/yr) with water supply (14%, $9M/yr), recreation (10%, $6.3M/yr), and transportation (14%, $8M/yr) following. The largest portion of the transportation benefit is for shipping. For the total AQPI system costs, which includes federal and other regional expenditures, the total initial costs are $66M initial and $3.3M annual O&M; these compute to a present value cost of $90M. Compared to present value benefit of $460M this computes to a B/C ratio of 5.1. Sensitivity analysis identified a range of B/C up to 13.7 and down to 1.7. It is important to acknowledge that many of the benefits are dependent on appropriate and adequate response by the hazards and water resources management agencies and citizens. L. E. JohnsonR. CifelliA. B. White2016-10-14T18:00:24Z2016-10-14T18:00:24Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1437This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14372016-10-14T18:00:24ZA comprehensive analysis of trends in extreme precipitation over southeastern coast of BrazilSoutheast Brazil (SE Brazil) is the most densely populated region in Brazil. Previous studies have shown evidence of positive trends in average precipitation and extreme events in a few locations, suggesting the increase in rainfall-related hazards with potential impacts to urbanized areas of SE Brazil. This study provides a comprehensive analysis of the spatial variability of trends in extreme precipitation over SE Brazil focusing on regional and local scales. We examine two daily rainfall datasets with more than 70 years of data: individual stations and gridded observed precipitation data. Our results indicate that the frequency of both rainy days and extreme daily precipitation events have increased in Sao Paulo state. Conversely, precipitation has become more concentrated in fewer events in Rio de Janeiro and Espirito Santo states where both data sets indicate positive trends in the intensity of extreme daily rainfall. The increases in frequency and intensity of extreme events have both contributed to positive trends in total seasonal and average daily precipitation over Sao Paulo. Additionally, the individual stations indicate negative trends in the number of light rainy days over large urbanized areas in the state of Sao Paulo. The spatial patterns of trends indicate that they are influenced by the proximity of large urban centres and topographic features, and also suggest variations and changes in the major climatic systems affecting precipitation regimes over SE.M. T. ZilliL. M. V. CarvalhoB. LiebmannM. A. S. Dias2016-10-14T17:57:21Z2016-10-14T17:57:21Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1436This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14362016-10-14T17:57:21ZAtmospheric conditions during the Arctic Clouds in Summer Experiment (ACSE): Contrasting open-water and sea-ice surfaces during melt and freeze-up seasons.The Arctic Clouds in Summer Experiment (ACSE) was conducted during summer and early autumn 2014, providing a detailed view of the seasonal transition from ice melt into freeze-up. Measurements were taken over both ice-free and ice-covered surfaces, near the ice edge, offering insight to the role of the surface state in shaping the atmospheric conditions. The initiation of the autumn freeze-up was related to a change in air mass, rather than to changes in solar radiation alone; the lower atmosphere cooled abruptly leading to a surface heat loss. During melt season, strong surface inversions persisted over the ice, while elevated inversions were more frequent over open water. These differences disappeared during autumn freeze-up, when elevated inversions persisted over both ice-free and ice-covered conditions. These results are in contrast to previous studies that found a well-mixed boundary layer persisting in summer and an increased frequency of surface-based inversions in autumn, suggesting that our knowledge derived from measurements taken within the pan-Arctic area and on the central ice-pack does not necessarily apply closer to the ice-edge. This study offers an insight to the atmospheric processes that occur during a crucial period of the year; understanding and accurately modeling these processes is essential for the improvement of ice-extent predictions and future Arctic climate projections.G. SotiropoulouM. TjernströmJ. Sedlar. . .P. O. G. Persson. . .M. D. ShupeP. E. JohnstonD. E. Wolfe2016-10-14T17:54:45Z2016-10-14T17:54:45Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1435This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14352016-10-14T17:54:45ZLinking atmospheric synoptic transport, cloud phase, surface energy fluxes, and sea-ice growth: observations of midwinter SHEBA conditionsObservations from the Surface Heat Budget of the Arctic Ocean (SHEBA) project are used to describe a sequence of events linking midwinter long-range advection of atmospheric heat and moisture into the Arctic Basin, formation of supercooled liquid water clouds, enhancement of net surface energy fluxes through increased downwelling longwave radiation, and reduction in near-surface conductive heat flux loss due to a warming of the surface, thereby leading to a reduction in sea-ice bottom growth. The analyses provide details of two events during Jan. 1–12, 1998, one entering the Arctic through Fram Strait and the other from northeast Siberia; winter statistics extend the results. Both deep, precipitating frontal clouds and post-frontal stratocumulus clouds impact the surface radiation and energy budget. Cloud liquid water, occurring preferentially in stratocumulus clouds extending into the base of the inversion, provides the strongest impact on surface radiation and hence modulates the surface forcing, as found previously. The observations suggest a minimum water vapor threshold, likely case dependent, for producing liquid water clouds. Through responses to the radiative forcing and surface warming, this cloud liquid water also modulates the turbulent and conductive heat fluxes, and produces a thermal wave penetrating into the sea ice. About 20–33 % of the observed variations of bottom ice growth can be directly linked to variations in surface conductive heat flux, with retarded ice growth occurring several days after these moisture plumes reduce the surface conductive heat flux. This sequence of events modulate pack-ice wintertime environmental conditions and total ice growth, and has implications for the annual sea-ice evolution, especially for the current conditions of extensive thinner ice.P. O. G. PerssonM. D. ShupeD. K. PerovichA. Solomon2016-10-14T17:52:24Z2016-10-14T17:52:24Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1434This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14342016-10-14T17:52:24ZMapping rainfall feedback to reveal the potential sensitivity of precipitation to biological aerosolsWe describe a tool to identify site-specific and seasonal effects of aerosols on rain from patterns in maps of rainfall feedback across regions with diverse topography and land use patterns.
The aerosols that influence the initiation and amount of precipitation are cloud condensation nuclei (CCN), giant CCN and ice nuclei. Aerosols are ever-present, their properties are variable and their abundance is dynamic. Therefore, the extent of their impact on the outcome of meteorological contexts that are favorable for rain are difficult to specify. Rainfall can generate aerosols. Those of biological origin that are generated after rainfall can accumulate in a persistent manner over several weeks. Based on a recently developed index of rainfall feedback that focuses on persistent feedback effects and that represents the a priori sensitivity of rainfall to aerosols – of biological origin in particular - we mapped the intensity and patterns of rainfall feedback at 1250 sites in the western US where 100-year daily rainfall data were available and where drought is critically severe. This map reveals trends in feedback related to orographic context, geographical location and season, among other trends. We describe an open-access tool (http://w3.avignon.inra.fr/rainfallfeedback/index.html) for mapping rainfall feedback on a planetary scale to provide a framework for future research to generate hypotheses and to establish rationale to choose field sites for experimentation. This will contribute to the long term goal of developing a robust understanding of specific and contextual aerosol effects on rainfall applicable to forecasting and to land use management.C. E. MorrisS. SoubeyrandE. K. BiggJ. M. CreameanD. C. Sands2016-10-14T17:50:11Z2016-10-14T17:50:11Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1433This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14332016-10-14T17:50:11ZThe representation of cumulus convection in high-resolution simulations of the 2013 Colorado Front Range FloodModel simulations of the 2013 Colorado Front Range floods are performed using 4-km horizontal grid spacing to evaluate the impact of using explicit convection (EC) versus parameterized convection (CP) in the model convective physics “gray zone”. Significant differences in heavy precipitation forecasts are found across multiple regions in which heavy rain and high-impact flooding occurred. The relative contribution of CP-generated precipitation to total precipitation suggests that greater CP scheme activity in areas upstream of the Front Range flooding may have led to significant downstream model error.
Heavy convective precipitation simulated by the Kain-Fritsch CP scheme in particular led to an alteration of the low-level moisture flux and moisture transport fields that ultimately prevented the generation of heavy precipitation in downstream areas as observed. An updated, scale-aware version of the Kain-Fritsch scheme is also tested, and decreased model errors both up- and down-stream suggest that scale-aware updates yield improvements in the simulation of this event. Comparison among multiple CP schemes demonstrate that there are model convective physics “gray zone” considerations that significantly impact the simulation of extreme rainfall in this event.K. M. Mahoney2016-10-14T17:48:36Z2016-10-14T17:48:36Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1432This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14322016-10-14T17:48:36ZMicrophysics-Regime Impacts on the Relationship between Orographic Rain and Orographic Forcing in the Coastal Mountains of Northern CaliforniaThis study examines the impact of microphysics regime on the relationship between orographic forcing and orographic rain in the coastal mountains of northern California using >4000 h of data from profiling Doppler radars, rain gauges and a GPS receiver collected over ten cool seasons. Orographic forcing is documented by hourly upslope flow, integrated water vapor (IWV) and IWV flux observed along the coast at Bodega Bay (BBY, 15 m MSL). Microphysics regime is inferred in the coastal mountains at Cazadero (CZC, 478 m MSL) where hourly periods of brightband (BB) rain and nonbrightband (NBB) rain are designated. BB rain is associated with a microphysics regime dominated by the seeder-feeder process while NBB rain is associated with a microphysics regime dominated by the warm-rain process. Mean BBY upslope flow, IWV and IWV flux are ~16%, ~5% and ~19% larger, respectively, for NBB rain compared to BB rain while mean CZC rain rate is ~33% larger for BB rain compared to NBB rain. The orographic enhancement ratio of CZC to BBY rain rate is 3.7 during NBB rain and 2.7 during BB rain. Rain rate at CZC increases as orographic forcing at BBY increases. For a given amount of BBY orographic forcing, mean CZC rain rates are larger for BB rain compared to NBB rain. Correlation coefficients associated with the relationship between CZC rain rate and BBY orographic forcing are smaller for NBB rain relative to BB rain, but these differences are not statistically significant.D. E. KingsmillP. J. NeimanA. B. White2016-10-14T17:46:56Z2016-10-14T17:46:56Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1431This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14312016-10-14T17:46:56ZUnderstanding rapid changes in phase partitioning between cloud liquid and ice in stratiform mixed-phase clouds: An Arctic Case StudyUnderstanding phase transitions in mixed-phase clouds is of great importance because hydrometeor phase controls the lifetime and radiative effects of clouds. In high latitudes, these cloud radiative effects have a crucial impact on the surface energy budget and thus on the evolution of the ice cover. For a springtime low-level mixed-phase stratiform cloud case from Barrow, Alaska, a unique combination of instruments and retrieval methods is combined with multiple modeling perspectives to determine key processes that control cloud phase partitioning. The interplay of local cloud-scale vs. large-scale processes is considered. Rapid changes in phase partitioning were found to be caused by several main factors. Major influences were the large-scale advection of different airmasses with different aerosol concentrations and humidity content; cloud-scale processes such as a change in the thermodynamical coupling state; and local-scale dynamics influencing the residence time of ice particles. Other factors such as radiative shielding by a cirrus and the influence of the solar cycle were found to only play a minor role for the specific case study (11-12 March 2013). For an even better understanding of cloud phase transitions, observations of key aerosol parameters such as profiles of cloud condensation nucleus and ice nucleus concentration are desirable.H. KalesseG. de BoerA. SolomonM. OueM. AhlgrimmD. ZhangM. D. ShupeE. LukeA. Protat2016-10-14T17:42:52Z2016-10-14T17:42:52Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1430This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14302016-10-14T17:42:52ZComparison of Global Precipitation Estimates across a Range of Temporal and Spatial ScalesCharacteristics of precipitation estimates for rate and amount from three global high-resolution precipitation products (HRPPs), four global climate data records (CDRs), and four reanalyses are compared. All datasets considered have at least daily temporal resolution. Estimates of global precipitation differ widely from one product to the next, with some differences likely due to differing goals in producing the estimates. HRPPs are intended to produce the best snapshot of the precipitation estimate locally. CDRs of precipitation emphasize homogeneity over instantaneous accuracy. Precipitation estimates from global reanalyses are dynamically consistent with the large-scale circulation but tend to compare poorly to rain gauge estimates since they are forecast by the reanalysis system and precipitation is not assimilated. Regional differences among the estimates in the means and variances are as large as the means and variances, respectively. Even with similar monthly totals, precipitation rates vary significantly among the estimates. Temporal correlations among datasets are large at annual and daily time scales, suggesting that compensating bias errors at annual and random errors at daily time scales dominate the differences. However, the signal-to-noise ratio at intermediate (monthly) time scales can be large enough to result in high correlations overall. It is shown that differences on annual time scales and continental regions are around 0.8 mm day−1, which corresponds to 23 W m−2. These wide variations in the estimates, even for global averages, highlight the need for better constrained precipitation products in the future.M. GehneT. M. HamillG. N. KiladisK. E. Trenberth2016-10-14T17:38:25Z2016-10-14T17:38:25Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1429This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14292016-10-14T17:38:25ZCoyote unmanned aircraft system observations in Hurricane Edouard (2014)Horizontal wind, temperature, and moisture observations are presented from two Coyote unmanned aircraft system (UAS) flights in the boundary layer of Hurricane Edouard (2014). The first flight sampled the meteorological conditions in the eye and eyewall at altitudes from 900 to 1500 m while Edouard was a major hurricane (105 kt) on 16 September 2014. The following day, a second Coyote sampled the inflow layer outside of the storm core at ~760 m altitude, when Edouard had weakened to an 80-kt hurricane. These flights represent the first deployments of a UAS from an airborne manned aircraft into a tropical cyclone. Comparisons between the Coyote data and the Lockheed WP-3D Orion (WP-3D) flight-level measurements and analyses constructed from dropsonde data are also provided. On 16 September 2014, the Coyote-measured horizontal wind speeds agree, on average, to within ~1 m s−1 of the wind speeds observed by the WP-3D and reproduce the shape of the radial wind profile from the WP-3D measurements. For the inflow layer experiment on 17 September, the mean wind speeds from the Coyote and the dropsonde analysis differ by only 0.5 m s−1, while the Coyote captured increased variability (σ = 3.4 m s−1) in the horizontal wind field compared to the dropsonde analysis (σ = 2.2 m s−1). Thermodynamic data from the Coyote and dropsondes agree well for both flights, with average discrepancies of 0.4°C and 0.0°C for temperature and 0.7°C and 1.3°C for dew point temperature on 16 and 17 September, respectivelyJ. J. CioneE. A. KalinaE. W. UhlhornA. M. FarberB. Damiano2016-10-14T17:32:01Z2016-10-14T17:32:01Zhttp://www.esrl.noaa.gov/psd/pubs/id/eprint/1428This item is in the repository with the URL: http://www.esrl.noaa.gov/psd/pubs/id/eprint/14282016-10-14T17:32:01ZGlobal Meteorological Drought: A Synthesis of Current Understanding with a Focus on SST Drivers of Precipitation DeficitsDrought affects virtually every region of the world, and potential shifts in its character in a changing climate are a major concern. This article presents a synthesis of current understanding of meteorological drought, with a focus on the large-scale controls on precipitation afforded by sea surface temperature (SST) anomalies, land surface feedbacks, and radiative forcings. The synthesis is primarily based on regionally focused articles submitted to the Global Drought Information System (GDIS) collection together with new results from a suite of atmospheric general circulation model experiments intended to integrate those studies into a coherent view of drought worldwide. On interannual time scales, the preeminence of ENSO as a driver of meteorological drought throughout much of the Americas, eastern Asia, Australia, and the Maritime Continent is now well established, whereas in other regions (e.g., Europe, Africa, and India), the response to ENSO is more ephemeral or nonexistent. Northern Eurasia, central Europe, and central and eastern Canada stand out as regions with few SST-forced impacts on precipitation on interannual time scales. Decadal changes in SST appear to be a major factor in the occurrence of long-term drought, as highlighted by apparent impacts on precipitation of the late 1990s “climate shifts” in the Pacific and Atlantic SST. Key remaining research challenges include (i) better quantification of unforced and forced atmospheric variability as well as land–atmosphere feedbacks, (ii) better understanding of the physical basis for the leading modes of climate variability and their predictability, and (iii) quantification of the relative contributions of internal decadal SST variability and forced climate change to long-term drought.S. D. SchubertR. E. StewartH. Wang. . .M. P. Hoerlinget al.